Field of the Invention
The present invention relates to a CVT drive train having a drive, a start-up element, a continuously variable variator, and a differential. In addition, the invention relates to a method for operating such a CVT drive train.
Description of the Related Art
The term CVT refers to a stepless transmission; the letters CVT stand for continuously variable transmission. To increase the transmission ratio range of a stepless transmission—its gear ratio spread—it is known from European published application EP 2 275 709 A1 to position a planetary transmission after the stepless transmission. The controllable planetary transmission enables two-range shifting and shifting into reverse. In addition, it is known from German published application DE 102 61 900 A1 to provide a multi-range CVT with fixed engageable gears, for example for moving off or for top speed; however, when these fixed transmission ratios are in operation, the variator is uncoupled. Consequently there is only one stepless range; stepless operation is not possible in all driving ranges.
An object of the present invention is to simplify the construction and/or the operation of a CVT drive train having an input drive, a start-up element, a continuously variable variator, and a differential.